There has hitherto been developed a method of producing a chemical, for example, ethanol, succinic acid, 1,4-butanediol, etc., from a biomass resource by means of fermentation. In the case of using a nonedible biomass resource, a furfural compound which is formed from a hemicellulose or the like becomes a fermentation-inhibiting component. For that reason, conventionally, it was general that the furfural compound is removed as an impurity. However, from the viewpoint of efficiently using the biomass resource, a technique of producing a chemical from a furfural which is formed from a hemicellulose is considered to be necessary.
A technique of extracting a furfural compound from a biomass resource has been studied from long ago. The furfural compound is also industrially produced as a raw material of a furan resin or the like. As other chemicals, for example, it may be considered to use the furfural compound as a raw material for producing a furan compound (tetrahydrofuran) therefrom. However, as for the furfural compound to be used as a raw material for producing a furan resin, in the production of such a chemical, a furfural compound having a higher purity is required.
There has hitherto been known a method of producing furan through a decarbonylation reaction from furfural in the presence of a catalyst (for example, Patent Literature 1). In addition, as a method of stably converting furfural into furan to produce the furan in a high efficiency, for example, Patent Literature 2 discloses a method in which in producing furan from furfural through a gas phase flow reaction, impurities which cause a lowering of the catalytic activity in crude furfural, specifically a sulfur component and so on are previously removed by means of distillation, adsorption separation, or the like, to obtain a raw material furfural having an acid value of a fixed value or less, which is then subjected to a decarbonylation reaction step.
In addition, in producing furan from furfural, as a method of purifying the furfural as a raw material in advance, Patent Literature 3 discloses a method in which after carrying out the treatment with a base in advance, distillation purification is performed.